The present invention relates to a magnetoresistive (MR) head and, more particularly, to an MR head desirably operable as a playback head for reading a magnetic disk.
An MR head is formed of NiFe, NiCo or similar ferromagnetic material. This type of head is based on a so-called MR effect, i.e., the fact that the ferromagnetic material changes its resistance depending on an angle between the direction of a current which flows through the ferromagnetic material and the direction of magnetization in the material. The MR effect is characterized in that the magnitude of a signal output depends only on the intensity of magnetic field and does not depend on the transition ratio of magnetic field. Hence, the signal output does not fall even when the relative speed between the head and a magnetic medium is reduced. For this reason, a MR head is a promising playback head for small magnetic disks.
Ideally, an MR element included in the MR head should operate under a single magnetic domain condition. Should a plurality of magnetic domains exist in the MR element, the rotation of magnetization relative to the signal field would be irregular since the direction of magnetization would differ from one magnetic domain to another. On the other hand, when the magnetic wall shifts in response to a change in the intensity of signal field, so-called Barkhausen noise is produced. The distortions of signal output and Barkhausen noise aggravate the error rate of signals read out by the MR head and, therefore, have to be reduced or fully eliminated.